There are certain qualities that all the good song melodies have. Such as:
In order to be considered a good melody, all the factors should be completely integrated and should be moving along a straight line. This is particularly important in majestic music that is used to evoke emotions.
Stepwise motion is good, but it gets too predictable, and finally boring, which affects the energy of the song. A melody will be considered good if it has occasional leaps and an upward surge because that enhances the interest of the audience.
Good Chord Progressions
The chord movement should be great if one wants to keep the attention of the audience.
Repetition Is Important
A little predictability is good so that the audiences can easily recall what they heard.
Climax is Vital
It is important for a melody to have a climactic moment because that too helps in keeping the attention of the audience.